Field of Invention
The present invention relates to a robotic arm suction cup capable of eliminating negative pressure, and more particularly to a robotic arm having two suction cups of unequal length able to eliminate negative pressure in the suction cups when a playing card is released from the suction cups for the game to go on smoothly.
Description of Related Arts
As shown in FIGS. 1, 2 and 3, in order to prevent players from touching playing cards, a shuffling machine 10 and a robotic arm 20 having a suction cup 21 are provided for playing a game. The suction cup 21 is connected with a vacuum pump 23 having a solenoid valve 24 through a communication tube 22. The shuffling machine 10 is formed with a central accommodation trough 11, a left accommodation trough 12, and a right accommodation trough 13. The playing cards 1 can be shuffled and stacked by the shuffling machine 10, and then the suction cup 21 of the robotic arm 20 is used to suck and place the playing cards in the central accommodation trough 11, the left accommodation trough 12, and the right accommodation trough 13, respectively. During the game, the playing cards 1 are completely operated by the machine, without any manual step, to avoid any fraud caused by personal factors. When the game is going on, the suction cup 21 is moved to be over the playing card 1, and the solenoid valve 24 is opened so that the vacuum pump 23 expels the air in the suction cup 21 and the communication pipe 22 to form a negative pressure state. The suction cup 21 sucks the playing card 1 from the central accommodation trough 11 and displays the playing card 1 to the player, and then the playing card 1 is recycled to the left accommodation trough 12 or the right accommodation trough 13 successively. For the playing card 1 to separate from the suction cup 21 and fall into the left accommodation trough 12 or the right accommodation trough 13, the solenoid valve 24 is closed and the vacuum pump 23 stops sucking. At this time, the suction cup 21 has residual negative pressure therein. In general, the surface of the playing card 1 is not absolutely airtight and the air gradually enters from the periphery of the suction cup 21 until the pressure between the suction cup 21 and the playing card 1 becomes normal pressure and the playing card 1 is detached from the suction cup 21 to fall. The required time is too long. As a result, the player will reduce his/her will to play the game. In view of this, how to quickly eliminate the negative pressure between the playing card 1 and the suction cup 21 needs to be improved. Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve these problems.